An integrated circuit may include a protective circuit connected to an input/output (I/O) pad to shunt electrostatic discharges away from other circuits. Electrostatic discharges are voltage transients which are commonly outside the operating voltage range of input and output signals of the integrated circuit. Negative voltage excursions, that is, voltage transients below the lower limit of the operating voltage range of the integrated circuit, may be shunted to the substrate of the integrated circuit through a simple diode in which the cathode is connected to the I/O pad and the anode is connected to, or is part of, the substrate. It may be desirable to pass positive signals within the operating voltage range to the other circuits while shunting positive voltage excursions higher than the operating voltage range away from the other circuits. Providing both functions may require a more complicated device than a simple diode. It may also be desirable to integrate the device providing positive voltage excursion protection into the integrated circuit without adding process steps.